Waning protection following 5 doses of a 3-component diphtheria,tetanus, and acellular pertussis vaccine

BackgroundThe effectiveness of diphtheria, tetanus, and acellular pertussis (DTaP) vaccines wanes substantially after the 5^th dose given at ages 4–6 years, but has not been described following 5 doses of the same type of DTaP vaccine. We investigated waning effectiveness against pertussis in California over nearly 10 years, which included large pertussis outbreaks, following 5 doses of GSK DTaP vaccines (DTaP₃).MethodsWe conducted a case-control study (NCT02447978) of children who received 5 doses of DTaP at Kaiser Permanente Northern California from 01/2006 through 03/2015. We compared time since the 5^th dose in confirmed pertussis polymerase chain reaction (PCR)-positive cases with pertussis PCR-negative controls. We used logistic regression adjusted for calendar time, age, sex, race, and service area to estimate the effect of time since the 5^th DTaP dose on the odds of pertussis. Our primary analysis evaluated waning after 5 doses of DTaP₃. We also examined waning after 5 doses of any type of DTaP vaccines.ResultsOur primary analysis compared 340 pertussis cases diagnosed at ages 4–12 years with 3841 controls. The any DTaP analysis compared 462 pertussis cases with 5649 controls. The majority of all DTaP doses in the study population were DTaP₃ (86.8%). Children who were more remote from their 5^th dose were less protected than were children whose 5^th dose was more recent; the adjusted odds of pertussis increased by 1.27 per year (95% CI 1.10, 1.46) after 5 doses of DTaP₃ and by 1.30 per year (95% CI 1.15, 1.46) after any 5 DTaP vaccines doses.ConclusionsWaning protection after DTaP₃ was similar to that following 5 doses of any type of DTaP vaccines. This finding is not unexpected as most of the DTaP vaccines administered were DTaP_3. Following 5 doses of DTaP₃ vaccines, protection from pertussis waned 27% per year on average.NCT number: NCT02447978.